In the field of video editing, it is often necessary to locate a specific video frame on a video tape. This is sometimes difficult to accomplish since typical consumer devices do not track tape position accurately through repeated transport control operations, such as fast-forward and rewind. Repeated transport control operations can result in the alignment of the videotape being off of its original position, sometimes by several frames. Furthermore, some devices, such as VHS-camcorders, do not provide tape position information through an external interface and can only be controlled via infrared commands, which do not provide any feedback of the tape position or of the current state of the device. In these cases, some other form of accurately tracking tape position is even more important. Some professional video equipment and some expensive consumer equipment support tape time code for accurate tape position indication.
In the prior art, U.S. Pat. No. 5,642,285 to Woo et al., discloses a GPS navigation receiver with a data output port for communicating a position estimate frame-by-frame and time codes in SMPTE format. A data logger records the position estimates with their corresponding time in time code format frame-by-frame in a database. U.S. Pat. No. 5,532,773 to Shaw et al., discloses a method of applying variable, momentous production information to each frame of a continuous visual image medium at the instant of use or after use, without interfering with the formation or display of the normal visual image on the same frame. The recorded production information becomes absolute reference points on the continuous visual image medium, enabling fast and accurate identification and retrieval at a later date.
U.S. Pat. No. 5,587,789 to Lee et al., discloses an apparatus and method for controlling recording and reproduction in a video cassette tape recorder. The apparatus is capable of, in a recording mode, separating specific data for speed-varied reproduction from compressed digital video signals, recording them on designated tracks, recording position information of the designated tracks on a control track by an index head or by recording position information of recording position synchronized blocks at the starting portions of the designated tracks recorded with the specific data.
An object of the invention is to devise a method of accurate tape position indication that can be used with inexpensive equipment without time code.